The present invention relates generally to objects which may be subjected to forcible collisions, and particularly to structures which are adapted to withstand impacts as well as structures which are adapted to deliver impacts.
Throughout history, collisions of solid objects have been extensively utilized in the development of civilizations. Impact processes are involved in a diversity of historical inventions ranging from hammers and anvils to cannonballs and armor plating. In the field of armor plating, most of the inventive efforts in recent years have been directed to creating lightweight and inexpensive armor plates for military applications. In this respect it has been found that ceramics when employed in a composite armor plate structure are useful in achieving these objectives. Reference may be had to the U.S. Pat. No. 3,509,833, entitled "Hard Faced Ceramic and Plastic Armor", issued to Cook on May 5, 1970, and to the U.S. Pat. No. 3,705,558, entitled "Armor", issued to McDougal et al, for a detailed treatment of the use of ceramics in armor plate structures.
Although ceramics provide a relatively lightweight material from which armor plate structures may be constructed, the principle objective of the armor is, of course, to defeat a specific projectile traveling at a specific speed. The term defeat in this context does not merely means stopping the projectile from penetrating the armor plate structure. Even though the projectile may not penetrate the armor, the armor plate structure may typically fracture in such a way as to cause a spall or fragment to fly off the back of the structure. The destructive consequences of this type of fracture are readily apparent when the armor is used to protect a confined area, as a tank or the like. Accordingly, an understanding of the fracture modes for armor plate structures is important in providing a truly effective armor plate structure, which is also lightweight and inexpensive.
From an investigation of the fracture or failure modes of impact structures, the applicant has developed a three dimensional shock wave theory which is set forth in the detailed description below. This shock wave theory characterizes a basic conceptual mechanism causing fracture, and is believed to account for the seemingly capricious manner in which certain impacted structures fracture. Briefly, shock waves may result from a dual path phenomena involving constructive interference reinforcement loci upon intersection of two sinusoidal phase related sonic velocity wave train components. These resulting shock waves are frequently hyperbolic in nature. The initial sonic velocity waves are derived from the fracture of or plastic deformation within a material. Depending upon the type and structure of the material these sonic velocity waves may produce a family of spatially distinct shock wave reinforcing intersection locus surfaces. This family of surfaces may comprise a surface for each Fourier frequency spectral component of the complex wave form. Phase velocity along each such locus or intersection surface represents a component of shock wave velocity, is always supersonic, changes as the disturbance moves along the locus surface and may differ in both velocity and wavelength from that along adjacent surfaces of the family which may comprise a shock wave. This shock wave theory in combination with well known optical and reflection laws provide the basis for creating a wide variety of superior impact structures from armor plates and kinetic energy projectiles to hammers and forging dies.
Accordingly, it is a principle object of the present invention to provide a novel structure adapted to withstand impacts.
It is a more specific object of the present invention to provide a lightweight and inexpensive armor plate structure capable of defeating projectiles traveling over a predetermined speed range.
It is an additional object of the present invention to provide a structure capable of returning a large portion of the energy delivered to the structure by the collision with a projectile or an object back to the area of collision for causing fractures in the projectile or object.
It is another principle object of the present invention to provide a novel structure adapted to deliver impacts to relatively slow moving or stationary objects.
It is a more specific obejct of the present invention to provide a projectile capable of rapidly delivering its kinetic energy into engagement with an object after its initial contact with the object.
It is another object of the present invention to provide a pair of impact structures adapted to fracture, deform, strike or shape an object in a more efficient manner.
To achieve the foregoing objects, the present invention generally provides an impact resisting structure formed with means for preventing the reinforcing intersection of a sonic wave train with its own reflection within the structure, such that at least one shock wave fracture mode is eliminated. More specifically, the structure is formed with means for suppressing the specular reflection of high frequency energy at one or more surfaces of the structure. This means may comprise irregularities formed in a surface to roughen the surface in a predetermined relationship with the wavelength of the sonic energy. These irregularities operate to modify the reflection of the sonic waves such that the reflection of the sonic waves back into the material is diffuse, thereby significantly reducing the amplitude of the reflected sonic waves in what would otherwise be a specular direction. In contrast to this randomly rough surface, the aboveidentified means may also comprise a systematically rough or retroreflective surface. The retroreflective surface operates to reflect the sonic energy waves on paths generally parallel to the paths in which the sonic energy waves were transmitted through the structure. Additionally, the structure may comprise a plurality of adjacently disposed plates, each having a different predetermined acoustic impedance, such that the sonic energy wave train may be diffused as it propagates through the structure.
The present invention further provides a structure adapted to deliver impacts to a relatively slow moving or stationary object. This structure may comprise a projectile having a jacket and a spline supported therein for providing a high velocity channel through which a sonic energy wave train may propagate. The high velocity channel operates to modify the rate at which the kinetic energy of the projectile is delivered to the object after its initial contact with the object.
Additional advantages and features of the present invention will become apparent from a reading of the detailed description of the preferred embodiments which makes reference to the following set of drawings in which: